In the sense that I could create points which are either only controller by scripts or by a user. For example, we read some pulses from meters and then need to multiply those pulses by some factor which would be nice to just store in some variable. Would that be best accomplished by using a Virtual data point with the "no change" set?
Does the concept of "internal points" exist in Mango?
Yes. There are LOTS of options!
For a simple transformation, where you'll want live updates to the transformed point, you should use a meta point with the point it's a transform of as its context point, set to update context. Then you can use the script body to transform the value. Meta points are added to Meta Data Sources.
Of near equivalence would be using a virtual point with polling disabled on its data source (Mango 3.0+, or its change type set to no change as you suggested), then create a "Point Link" from the point to be transformed to the virtual point that will receive the value.
Also Scripting Data sources have points that can hold transformed or processed values, but typically a scripting data point will hold some kind of runtime information, where meta points will hold analysis type information, and virtual points will hold interface information or user supplied information, for instance. But, they're mostly malleable enough any of them could be used. I'd recommend the Meta Data Source.
What we call "internal" points are points about the state of the Mango or computer, and those are on the "Internal Data Source"